Concrete wall forms are well known in the art and generally comprise a series of form sections which may be joined together in an edge-to-edge relationship and arranged in a spaced, parallel arrangement with respect to a second series of form sections to define a space for receiving poured wet concrete therebetween. One particular type of wall form shown and described herein, comprises a composite form having a metal frame and a planar facing member secured to the frame. The frame may be of steel or aluminum and the facing member generally comprises a laminated plywood panel sized to fit the frame. Examples of this type of form have been manufactured and sold by Symons Corporation of Des Plaines, Ill. under the trademarks STEEL-PLY® and ALISPLY™. Because these forms are relatively light in weight, they are particularly suited to use where the forms are handled manually, such as in the construction of residential structures for example.
In use, the spaced parallel form sections are maintained in their proper relationship by tie rods which span the space between the parallel form sections and are secured to the oppositely facing forms. One type of tie system commonly used in the United States utilizes frangible tie rods formed from metal wire or flat metal strips, such as those disclosed in U.S. Pat. Nos. 2,580,330 and 2,948,045, assigned to the assignee of the present invention and incorporated herein by reference in their entirety. These frangible ties generally have reduced portions along their length that define opposed ends which may be broken off and removed from the cured concrete structure while a central portion of the tie remains embedded therein. A different type of tie system, which is popular in European countries, as well as in Canada and South America, utilizes a threaded bar which extends between the parallel form sections. The threaded bar may be secured to the respective forms by a nut tightened over the threaded bar. The bar passes through a tube, generally formed from PVC, and the tube protects the threaded rod from contact with the poured concrete. After the concrete has cured, the tube remains embedded in the concrete structure but the bar may be removed for subsequent use.
While both types of tie systems have been used for many years, prior concrete forms are generally configured to utilize only one type or the other. Accordingly, contractors or builders are limited to using the tie system to which their forms have been manufactured for use. Therefore, if it is desired to utilize a different tie system, either because of customer requirements or otherwise, the forms must be significantly modified or else new forms purchased to accommodate the desired tie system.
There is thus a need for a concrete form which is capable of utilizing various form tie systems.